1. Technical Field
The present invention relates to an electro-optical device such as a liquid crystal device or the like. In addition, the invention further relates to an electronic apparatus that is provided with an electro-optical device. An example of a variety of electronic apparatuses to which the invention can be applied includes but not limited to a liquid crystal projector.
2. Related Art
As a typical configuration example thereof, an electro-optical device of the related art has a plurality of data lines and a plurality of scanning lines that are formed so as to intersect with each other in an image display region (i.e., image display area) over a substrate. A plurality of pixel electrodes are arrayed in a matrix pattern in such a manner that each of the plurality of pixel electrodes is provided at a position corresponding to the intersection of the data line and the scanning line. Each of the plurality of pixel electrodes is switch-controlled on a pixel-by-pixel basis (i.e., for each pixel). Each of the plurality of pixels is provided with a transistor, which is an example of a pixel-switching element that controls the corresponding one of the plurality of pixel electrodes. Each of the plurality of pixel-switching transistors has a lightly doped drain structure, which is hereafter abbreviated as an LDD structure.
An electro-optical device of the related art that is described in JP-A-2005-45017 is provided with a lower light-shielding film. The lower light-shielding film, which is formed over a substrate at a layer under the transistor, shuts off an incident light beam that enters and propagates toward the semiconductor film of the transistor through a lower layer(s) that is provided below the semiconductor film of the transistor. Another electro-optical device of the related art that is described in Japanese Patent No. 3,307,144 is provided with an upper light-shielding film. The upper light-shielding film, which is formed over a substrate at a layer over the transistor, shuts off an incident light beam that enters and propagates toward the semiconductor film of the transistor through upper layers that are provided above the semiconductor film of the transistor. Each of the related-art electro-optical devices described in JP-A-2005-45017 and Japanese Patent No. 3,307,144 has a disadvantage in that it has relatively weak light-shielding protection/structure against light that enters and propagates toward the side of the LDD regions of a semiconductor layer, or, in other words, lateral light that enters and propagates toward the LDD regions of a semiconductor layer. Because of such vulnerability to lateral light, each of the related-art electro-optical devices described in JP-A-2005-45017 and Japanese Patent No. 3,307,144 is susceptible to the occurrence of an optical leakage current, which should be avoided.
In an effort to provide a technical solution to such a problem, in the technical field to which the present invention pertains, a technique for shutting off lateral light that enters and propagates toward (the side of) the LDD regions of a semiconductor layer has been proposed so far. An example of a related-art technique for shutting off such a laterally-propagating light beam is disclosed in the following publications, each of which is directed to an electro-optical device that uses LDD transistors: JP-A-2000-356787, JP-A-2004-170656, JP-A-2006-171136, and JP-A-2003-307725. Specifically, in the light-shielding structure of a transistor of the related art described in JP-A-2000-356787, JP-A-2004-170656, JP-A-2006-171136, and JP-A-2003-307725, a contact hole is formed at each side of a semiconductor film along a channel region and LDD regions thereof when viewed in plan. An electro-conductive film (i.e., conductive film) that has light-shielding property is formed in the contact hole. The electro-conductive film that is formed inside the contact hole, or at least the inner-contact-hole portion thereof, is made of the same material and in the same single film formation process as that of, for example, a gate electrode. The electro-conductive film that is formed inside the contact hole makes it possible to shut off a lateral light beam, which enters and propagates toward the side of the LDD regions of a semiconductor layer as well as toward the channel region thereof.
The semiconductor film of an LDD-structure transistor has highly-doped (i.e., high concentration) impurity regions in addition to the LDD regions and the channel region mentioned above. As a typical layout thereof, the channel region is interposed between one of the LDD regions and the other thereof. The LDD-chanel-LDD region explained above is further interposed between one of the highly doped impurity regions and the other. The above-mentioned one of the highly doped impurity regions is electrically connected to a data line, whereas the above-mentioned other thereof is electrically connected to a pixel electrode.
The light-shielding structure of a transistor of the related art described in JP-A-2000-356787, JP-A-2004-170656, and JP-A-2006-171136 has a technical problem in that it is difficult to shut off a lateral incident light beam that enters and propagates toward the side of the electric-connection portion of each of the data-line-side highly doped impurity region and the pixel-electrode-side highly doped impurity region. Herein, the above-mentioned electric-connection sub region of the data-line-side highly doped impurity region is electrically connected to a data line, whereas the above-mentioned electric-connection sub region of the pixel-electrode-side highly doped impurity region is electrically connected to a pixel electrode. There is a relatively greater possibility of the occurrence of an optical leakage current in the pixel-electrode-side LDD region of the semiconductor layer of an LDD transistor than in the data-line-side LDD region thereof. For this reason, any lateral incident light beam that enters and propagates toward the side of the electric-connection sub region of the pixel-electrode-side highly doped impurity region might be irradiated to the pixel-electrode-side LDD region of the semiconductor layer of the LDD transistor, which is more susceptible to an optical leakage current. As a result thereof, the operation failure of the transistor might occur.
The light-shielding structure of a transistor of the related art described in JP-A-2003-307725 makes it possible to shut off a lateral incident light beam that enters and propagates toward the side of the electric-connection portion of each of the data-line-side highly doped impurity region and the pixel-electrode-side highly doped impurity region. However, in the light-shielding structure of a transistor of the related art described in JP-A-2003-307725, an extra light-shielding film that is formed at a layer different from that of a gate electrode extends into a contact hole. That is, in the light-shielding structure of a transistor of the related art described in JP-A-2003-307725, the inner-contact-hole portion of such an extra light-shielding film, which is not the same single layer as the gate electrode, shuts off a lateral incident light beam. For this reason, the light-shielding structure of a transistor of the related art described in JP-A-2003-307725 has a technical disadvantage in that it requires more complex manufacturing process.